Imaging system for thermal transfer

ABSTRACT

An optical imaging system is disclosed for selective thermal transfer of a material from a donor film to a substrate. The imaging system includes a light source assembly that is configured to emit a patterned light beam. The patterned light beam includes a plurality of discrete output light segments where the segments at most partially overlap. The imaging system further includes a light relay assembly that receives and projects the plurality of discrete output light segments onto a transfer plane so as to form a projected light segment by a substantial superposition of the plurality of discrete output light segments. When a donor film that includes a transferable material is placed proximate a substrate that lies in the transfer plane, the projected light segment is capable of inducing a transfer of the transferable material onto the substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/863,938, filed Jun. 9, 2004, now U.S. Pat. No. 7,148,957.

FIELD OF THE INVENTION

This invention generally relates to imaging systems. In particular, theinvention relates to laser induced thermal imaging systems fortransferring a material from a donor film to a substrate.

BACKGROUND

Pixelated displays are commonly used for displaying information.Examples include liquid crystal computer monitors and televisions, andorganic light emitting displays used in applications such as cellphones, and portable digital video displays. The pixels in a display canbe patterned using a variety of methods, such as photolithography,photoablation, and laser induced thermal imaging (LITI). LITI has beenparticularly applicable in patterning organic materials in organicelectronic displays or devices.

SUMMARY OF THE INVENTION

Generally, the present invention relates to imaging systems.

In one embodiment of the invention, an optical imaging system forselective thermal transfer of a material from a donor film to asubstrate includes a light source assembly that is configured to emit apatterned light beam. The patterned light beam includes a plurality ofdiscrete output light segments where the segments at most partiallyoverlap. The optical imaging system further includes a light relayassembly that receives and projects the plurality of discrete outputlight segments onto a transfer plane so as to form a projected lightsegment by a substantial superposition of the plurality of discreteoutput light segments. When a donor film that includes a transferablematerial is placed proximate a substrate that lies in the transferplane, the projected light segment is capable of inducing a transfer ofthe transferable material onto the substrate.

In another embodiment of the invention, an optical imaging system forselective thermal transfer of a material from a donor film to asubstrate includes a light source assembly that is configured to emit apatterned light beam. The patterned light beam includes an output arrayof discrete output light segments. The output array has n columns and mrows, n being greater than 1. The discrete output light segments in acolumn at most partially overlap. The optical imaging system furtherincludes a light relay assembly that receives and projects the outputarray onto a transfer plane so as to form a projected array of discreteprojected light segments in the transfer plane. The projected array hasn columns and one row. Each discrete projected light segment in aprojected column is formed by a substantially full overlap of thediscrete output light segments in a corresponding column of the outputarray, such that when a donor film that includes a transferable materialand is disposed proximate a carrier, is placed proximate a substratethat lies in the transfer plane, each of the discrete projected lightsegments is capable of inducing a transfer of the transferable materialfrom the carrier onto the substrate.

In another embodiment of the invention, an optical imaging system forselective thermal transfer of a material from a donor film to asubstrate includes a light source that is capable of emitting apatterned light beam. The patterned light beam includes two or moreemitted light segments. Each emitted light segment has a firstuniformity along a first direction. The optical imaging system furtherincludes a light homogenizer that receives the two or more emitted lightsegments and homogenizes each emitted light segment and transmits acorresponding homogenized light segment. Each transmitted homogenizedlight segment has a third uniformity along the first direction. Thethird uniformity of each transmitted homogenized light segment isgreater than the first uniformity of each corresponding emitted lightsegment. The optical imaging system further includes a mask thatreceives each of the transmitted homogenized light segments and patternseach transmitted homogenized light segment into a row of n discretelight subsegments along the first direction. n is greater than twenty.Each discrete light subsegment has a length along the first direction.The mask is capable of setting the length of each discrete lightsubsegment at any value in a range from about 50 microns to about 150microns with an accuracy of one micron or better. The optical imagingsystem further includes a substrate. The optical imaging system furtherincludes a first lens system that projects each row of n discrete lightsubsegments onto the substrate with a projection magnification of onealong the first direction, thereby forming a single row of n discreteprojected light segments along the first direction. The distance betweenthe first and the nth discrete projected light segments is at least 10mm. When a donor film that includes a transferable material and isdisposed proximate a carrier, is placed proximate the substrate betweenthe first lens and the substrate, each of the n discrete projected lightsegments is capable of inducing a transfer of the transferable materialfrom the carrier onto the substrate.

In another embodiment of the invention, an optical imaging system forselective thermal transfer of a material from a donor film to asubstrate includes a light source that includes two or more sets oflight bar assemblies. Each set of light bar assembly includes two ormore light bars. Each light bar in the set is capable of emittingpolarized light. A first polarization direction of polarized lightemitted from at least one light bar in the set is different than asecond polarization direction of polarized light emitted from at leastanother light bar in the set. A polarizing beam combiner uses thedifference between the first and second polarization directions tocombine polarized light emitted from the two or more light bars in theset to form a combined emitted light beam. A spatial filter combines thecombined emitted light beams from the two or more sets of light emittersby reflecting at least a combined emitted light beam from one set oflight emitters and transmitting at least a combined emitted light beamfrom another set of light emitters. The combination of the combinedemitted light beams form a patterned light beam. The patterned lightbeam includes one or more emitted light segments. Each emitted lightsegment has a first uniformity along a third direction. The opticalimaging system further includes a light homogenizer that receives theone or more emitted light segments and homogenizes each emitted lightsegment and transmits a corresponding homogenized light segment. Eachtransmitted homogenized light segment has a third uniformity along thethird direction. The third uniformity of each transmitted homogenizedlight segment is greater than the first uniformity of each correspondingemitted light segment. The optical imaging system further includes amask that receives and patterns each of the transmitted homogenizedlight segments into a row of n discrete light subsegments along thethird direction. n is greater than twenty. Each discrete lightsubsegment has a length along the third direction. The mask is capableof setting the length of each discrete light subsegment at any value ina range from about 50 microns to about 150 microns with an accuracy ofone micron or better. The optical imaging system further includes asubstrate. The optical imaging system further includes a first lenssystem that projects each row of n discrete light subsegments onto thesubstrate with a projection magnification of one along the thirddirection, thereby forming a single row of n discrete projected lightsegments along the third direction. The distance between the first andthe nth discrete projected light segments is at least ten millimeters.When a donor film that includes a transferable material that is disposedproximate a carrier, is placed proximate the substrate between the firstlens and the substrate, each of the n discrete projected light segmentsis capable of inducing a transfer of the transferable material from thecarrier onto the substrate.

BRIEF DESCRIPTION OF DRAWINGS

The invention may be more completely understood and appreciated inconsideration of the following detailed description of variousembodiments of the invention in connection with the accompanyingdrawings, in which:

FIG. 1 illustrates a block diagram of an imaging system in accordancewith one embodiment of the invention;

FIG. 2 illustrates a schematic three-dimensional view of an imagingsystem in accordance with one embodiment of the invention;

FIGS. 3A and 3B illustrate a schematic three-dimensional view of anemitted light segment before and after passing through a homogenizer,respectively;

FIGS. 4A and 4B illustrate beam uniformity along two differentdirections, for the emitted light segments shown in FIGS. 3A and 3B;

FIGS. 5A and 5B illustrate divergence of an emitted light segment alongtwo different directions;

FIGS. 6A and 6B illustrate divergence of a homogenized light segmentalong two different directions;

FIG. 7 illustrates a cross-sectional view of a portion of lightpatterned by a mask in accordance with one embodiment of the invention;

FIG. 8 illustrates a schematic side-view of superposition of lightpatterned by a mask in accordance with one embodiment of the invention;

FIG. 9 illustrates a schematic side-view of transferring a transferablematerial in accordance with one embodiment of the invention;

FIG. 10 illustrates a schematic side-view of a transferred transferablematerial in accordance with one embodiment of the invention;

FIG. 11 illustrates a schematic top-view of a mask in accordance withone embodiment of the invention;

FIG. 12 illustrates a schematic top-view of a mask in accordance withone embodiment of the invention;

FIG. 13 illustrates a schematic top-view of a mask in accordance withone embodiment of the invention;

FIG. 14 illustrates a schematic side-view of a mask having a pre-mask inaccordance with one embodiment of the invention;

FIG. 15 illustrates a schematic side-view of a mask assembly inaccordance with one embodiment of the invention;

FIG. 16 illustrates a schematic three-dimensional view of a light barassembly in accordance with one embodiment of the invention;

FIG. 17 illustrates a schematic three-dimensional view of a light barassembly in accordance with one embodiment of the invention;

FIG. 18 illustrates a schematic three-dimensional view of a light barassembly in accordance with one embodiment of the invention;

FIG. 19 illustrates a schematic three-dimensional view of a lightcombiner combining two sets of emitted light segments in accordance withone embodiment of the invention;

FIGS. 20A-C illustrate cross-sectional views of the two sets of emittedlight segments and the resulting combination of the two sets shown inFIG. 19;

FIG. 21 illustrates a schematic top-view of polarizing beam combinerscombining different sets of emitted light segments;

FIG. 22 illustrates a schematic three-dimensional view of a light sourceand a part of an imaging system in accordance with one embodiment of theinvention;

FIG. 23 illustrates a schematic side-view of a portion of an imagingsystem in accordance with one embodiment of the invention; and

FIG. 24 illustrates a block diagram of an imaging system in accordancewith one embodiment of the invention.

It will be appreciated that unless otherwise noted, the various drawingsare not drawn to scale.

DETAILED DESCRIPTION

The present invention generally applies to imaging systems. Theinvention is particularly applicable to laser induced thermal imagingsystems for patterning pixels in a display where it is desirable toaccomplish the patterning in a short amount of time to reduce, forexample, the processing cost.

In the specification, a same reference numeral used in multiple figuresrefers to same or similar elements having same or similar properties andfunctionalities.

FIG. 24 illustrates a block diagram of an imaging system 2400 inaccordance with one embodiment of the invention. Imaging system 2400includes a light source assembly 2410 and a light relay assembly 2420.

In one particular embodiment of the invention, output light 2415 oflight source assembly 2410 includes a patterned light beam where thepattern includes a plurality of discrete output light segments. Thediscrete light segments can be isolated from each other, meaning thatthere is little or no overlap between any two segments. In general, anytwo discrete output light segments at most partially overlap. Lightrelay assembly 2420 receives and projects the plurality of discreteoutput light segment onto transfer plane 2430 so as to form a projectedlight segment by a substantial superposition of the plurality ofdiscrete output light segments. The power of the projected lightsegments can be close to a sum of the powers of the plurality ofdiscrete output light segments. Furthermore, when a donor film thatincludes a transferable material disposed proximate a carrier, is placedproximate a substrate that lies in transfer plane 2430, the projectedlight segment is capable of inducing a transfer of the transferablematerial from the carrier onto the substrate.

In another embodiment of the invention, output light 2415 of lightsource assembly 2410 includes a patterned light beam where the patternincludes an output array of discrete output light segments, the outputarray having n columns and m rows, n being greater than 1. m can begreater than 1. The discrete output light segments in an array columncan be isolated from each other. In general, any two output lightsegments in an array column at most partially overlap. Light relayassembly 2420 receives and projects the output array onto transfer plane2430 so as to form a projected array of discrete projected lightsegments in the transfer plane. The projected array has n columns and asingle row where each discrete projected light segment in a column isformed by a substantially full overlap of the discrete output lightsegments in a corresponding column of the output array. When a donorfilm that includes a transferable material disposed proximate a carrier,is placed proximate a substrate that lies in the transfer plane, each ofthe discrete projected light segments is capable of inducing a transferof the transferable material from the carrier onto the substrate.

In another embodiment of the invention, output light 2415 of lightsource assembly 2410 includes a two-dimensional output array of discretelight subsegments, where the output array has n columns and m rows, nbeing greater than 1. The m rows are divided into p groups, each groupincluding at least two rows of discrete light subsegments, where no rowis included in more than one group. Light relay assembly 2420 transfersthe m by n array of discrete light subsegments onto transfer plane 2430by superposing all the rows in each group so as to form a projectedarray of projected light segments in transfer plane 2430, where theprojected array has n columns and p rows. Each projected light segmentis capable of inducing a transfer of a transferable material that iscoated on a carrier and placed proximate a substrate that lies intransfer plane 2430. In the case where p is 1, the m rows aresubstantially fully superposed forming a single row of n projected lightsegments.

FIG. 1 shows an exemplary block diagram of an imaging system 100 inaccordance to one aspect of the present invention where each blockdescribes a different component or sub-assembly in the imaging system.The imaging systems of the present invention need not necessarilyinclude all the blocks shown in FIG. 1. Furthermore, an imaging systemaccording to the present invention may have additional blocks not shownin FIG. 1. Imaging system 100 includes a light source 110, a firstoptical relay 120, a light homogenizer 130, a second optical relay 140,a mask 150, a third optical relay 160, and a substrate 170.

Imaging system 100 projects light provided by light source 110 ontosubstrate 170 so that, for example, the projected light is capable ofinducing a transfer of a transferable material that is coated on acarrier and placed proximate substrate 170, from the carrier ontosubstrate 170.

Imaging system 100 can be used to selectively transfer, and therefore,pattern a display component. For example, imaging system 100 may be usedto transfer emissive materials, color filters (e.g., red, green, andblue), black matrix, electrodes, transistors, insulators, and spacersonto a display substrate. An important characteristic of imaging system100 according to one embodiment of the present invention is highthroughput where throughput is the number of displays or displaycomponents patterned in a given unit of time, such as one hour. As such,throughput relates to the time required to pattern various displaycomponents, such as color filters and black matrix. A high throughput isgenerally desirable because it can result in lower processingmanufacturing costs, and hence, a less expensive final display product.

According to one embodiment of the invention, a characteristic ofimaging system 100 that is of particular importance in increasingthroughput is light intensity at substrate 170. In general, theintensity of light 105 at substrate 170 needs to be higher than athreshold value in order to induce a material transfer. Furthermore, forlight intensities above the threshold value, a higher light intensitygenerally results in a reduction in time required to transfer amaterial, such as a color filter material, from a donor film onto, say,a display substrate. As such, a light 105 having high intensity or powercan increase the overall throughput. The present invention providesvarious embodiments that are capable of significantly increasing thethroughput by delivering high beam intensities at substrate 170.

Another important characteristic of imaging system 100 according to oneembodiment of the invention is beam uniformity, especially at substrate170. A non-uniform light 105 can result in, for example, partial or notransfer of a transferable material, or damage to the transferablematerial or a nearby element. As such, a function of homogenizer 130according to one embodiment of the present invention is to improve beamuniformity in one or more directions.

Imaging system 100 further includes a mask 150 for receiving andpatterning an incident light 103 into an output light 104 patterned in adesired pre-determined pattern or shape. Preferably, a light patternproduced by mask 150 substantially matches, at least within a scalingfactor, a corresponding pixel design on a display so that all eventualtransfers induced by the light pattern occur at intended locationsresulting in good registration between the transfer and intendedlocations.

Imaging system 100 further includes a number of optical relays (forexample, as shown, a first optical relay 120, a second optical relay140, and a third optical relay 160). Each of these optical relays is, atleast in part, intended to transfer light from a previous block orsub-assembly to a next block or sub-assembly. For example, third opticalrelay 160 may be primarily designed to project light that is patternedby mask 150 onto substrate 170. As another example, first optical relay120 may be designed primarily to transfer light that is emitted by lightsource 110 to homogenizer 130. Each optical relay may include componentssuch as lenses, mirrors, retarders, beam splitters, beam combiners, andbeam expanders. Furthermore, one or more of the optical relays may alsoperform other functions such as collimation, magnification, imaging,focusing, or reduction in aberrations.

FIG. 2 illustrates a schematic three-dimensional view of an imagingsystem 200 in accordance with one particular embodiment of theinvention. Imaging system 200 includes a light source 210, a homogenizer230, a mask 250, a lens system 260, and a substrate 270.

Light source 210 emits a patterned light beam 215 that generallypropagates along a direction, such as the z-axis. Patterned light beam215 includes one or more emitted light segments. In the particularexample shown in FIG. 2, patterned light beam 215 includes three emittedlight segments 211A, 211B, and 211C, where each emitted light segmentpropagates along the z-axis and has a finite extent along at least onedirection that is normal to the direction of propagation of the lightsegment. In particular, each emitted light segment has a finite extentalong at least one of x- and y-directions for a direction of propagationalong the z-axis. In the exemplary embodiment shown in FIG. 2, each ofemitted light segments 211A, 211B, and 211C has finite extent along bothx- and y-directions. Each emitted light segment can have differentintensity or beam uniformity profiles along different directions. Inparticular, each of emitted light segments 211A, 211B, and 211C has abeam uniformity profile along the x-axis and a beam uniformity profilealong the y-axis, where x-, y-, and z-directions are mutuallyperpendicular to each other as shown in FIG. 2. In addition, eachemitted light segment can diverge, converge, or remain substantiallycollimated as it propagates along the z-axis. As such, each of emittedlight segments 211A, 211B, and 211C has a divergence angle along thex-axis and a divergence angle along the y-axis. In the invention,divergence of a light beam refers to an angular spread of the light beamat its full width at half intensity maximum (FWHM). Divergence and beamuniformity of each emitted light segment is further described inreference to FIGS. 3-5.

FIG. 3A shows a portion of emitted light segment 211A. A cross-sectionof emitted light segment 211A in the xy-plane, such as cross-section211A-1, can have a uniformity profile along the y-axis (direction AA′)and a uniformity profile along the x-axis (direction BB′). FIG. 4A showsuniformity profile 211A-y of emitted light segment 211A (incross-section 211A-1) along the y-axis. Similarly, FIG. 4B showsuniformity profile 211A-x of emitted light segment 211A (in the samecross-section 211A-1) along the x-axis. The vertical axes in FIGS. 4Aand 4B represent light intensity denoted by the letter I. The horizontaland vertical axes in FIGS. 4A and 4B are not drawn to scale. In theexamples shown in FIGS. 4A and 4B, emitted light segment 211A has afairly non-uniform intensity profile 211A-y along the y-axis and aGaussian intensity profile 211A-x along the x-axis. Emitted lightsegment 211A can have other intensity profiles along the x-axis such aflat-top or uniform profile, or any other profile that may beadvantageous in an imaging application. Furthermore, imaging system 200may include an optical device to convert one intensity profile intoanother intensity profile. For example, imaging system 200 may includean optical device to convert a Gaussian intensity profile into a uniformor flat-top intensity profile. One such optical device for transforminga non-uniform intensity profile, such as a Gaussian profile, into auniform intensity profile is disclosed in U.S. Pat. No. 6,654,183.

FIGS. 5A and 5B illustrate divergence of emitted light segment 211Aalong two different directions. In particular, FIG. 5A illustratesdivergence of emitted light segment 211A in the y-z plane, or thedivergence along the y-direction as the light segment propagates alongthe z-axis. α₁ is the full divergence angle of emitted light segment211A along the y-axis. Similarly, FIG. 5B illustrates divergence ofemitted light segment 211A in the x-z plane, or the divergence along thex-direction as the light segment propagates along the z-axis. α₂ is thefull divergence angle of emitted light segment 211A along the x-axis.

Referring back to FIG. 2, homogenizer 230 receives patterned light 215from its input face 230A. Homogenizer 230 is designed, at least in part,to improve beam uniformity of each emitted light segment of receivedpatterned light 215 in one or more directions. In particular,homogenizer 230 is primarily designed to improve uniformity of eachreceived emitted light segment along the y-axis. For example,homogenizer 230 is designed to improve uniformity of emitted lightsegment 211A (within the extent of the light segment) along the y-axis,which is the intensity profile 211A-y shown in FIG. 4A. Each of emittedlight segments 211A, 211B, and 211C is homogenized by homogenizer 230along y-axis. Although homogenizer 230 may homogenize a received emittedlight segment along more than one direction, in one particularembodiment of the invention, homogenizer 230 homogenizes each receivedemitted light segment along the y-direction, but not along thex-direction. As such, according to one particular embodiment of theinvention, homogenizer 230 homogenizes patterned light beam 215 along afirst direction but not along a second direction, where the firstdirection is different than the second direction.

Homogenizer 230 transmits each homogenized emitted light segment fromits output face 230B resulting in a homogenized patterned light beam 235that includes transmitted homogenized light segments 231A, 231B, and231C, where light segment 231A corresponds to light segment 211A, lightsegment 231B corresponds to light segment 211B, and light segment 231Ccorresponds to light segment 211C. In the exemplary embodiment shown inFIG. 2, homogenized patterned light beam 235 propagates along thez-axis, although, in general, homogenized patterned light beam 235 maypropagate in a different direction, where the change in direction(relative to patterned light beam 215) may be caused by, for example,homogenizer 230.

A cross-section of each of transmitted homogenized light segments 231A,231B, and 231C has a beam uniformity profile along the x-axis and a beamuniformity profile along the y-axis. In addition, each transmittedhomogenized light segment can diverge, converge, or remain substantiallycollimated as it propagates along the z-axis. As such, each oftransmitted homogenized light segments 231A, 231B, and 231C has adivergence angle along the x-axis and a divergence angle along they-axis. Divergence and beam uniformity of each transmitted homogenizedlight segment is further described in reference to FIGS. 3, 4, and 6.

FIG. 3B shows a portion of homogenized light segment 231A. Across-section of homogenized light segment 231A in the xy-plane, such ascross-section 231A-1, can have a uniformity profile along the y-axis(direction CC′) and a uniformity profile along the x-axis (directionDD′). FIG. 4A shows a uniformity profile 231A-y of homogenized lightsegment 231A (in cross-section 231A-1) along the y-axis. It can be seenthat 231A-y is more uniform than 211A-y within the general extent of thelight segment along the y-axis. Similarly, FIG. 4B shows uniformityprofile 231A-x of light segment 231A (in the same cross-section 231A-1)along the x-axis. It can be seen that intensity profiles 211A-x and231A-x essentially overlap. As such, homogenizer 230 has homogenizedemitted light segment 211A along the y-axis, but has not significantlychanged the uniformity of emitted light segment 211A along the x-axis.

According to one embodiment of the invention, the uniformity of ahomogenized light segment along the y-axis is preferably at least 10times greater, more preferably at least 20 times greater, and even morepreferably at least 30 times greater, than a corresponding emitted lightsegment.

FIGS. 6A and 6B illustrate divergence of transmitted homogenized lightsegment 231A along two different directions. In particular, FIG. 6Aillustrates divergence of transmitted homogenized light segment 231A inthe y-z plane, or the divergence along the y-direction as the lightsegment propagates along the z-axis. α′₁ is the full divergence angle oftransmitted homogenized light segment 231A along the y-axis. Similarly,FIG. 6B illustrates divergence of transmitted homogenized light segment231A in the x-z plane, or the divergence along the x-direction as thelight segment propagates along the z-axis. α′₂ is the full divergenceangle of emitted light segment 211A along the x-axis.

In general, α₁ and α′₁ need not be equal. Similarly, α₂ and α′₂ need notbe equal. According to one aspect of the invention, however, α₂ and α′₂are equal, but α₁ and α′₁ are not equal. As such, according to thisparticular aspect of the invention, homogenizer 230 changes thedivergence angle of each emitted light segment along the y-direction,but not along the x-direction. According to another aspect of theinvention, α₂ and α′₂ are equal, and α₁ and α′₁ are also equal. In someembodiments of the invention, as shown in FIG. 23, an optical relay 2310(such as optical relay 120 in FIG. 1) is disposed between light source210 and homogenizer 230. FIG. 23 illustrates a schematic side-view of aportion of an imaging system in accordance with one particularembodiment of the invention. In particular, FIG. 23 shows an opticalrelay 2310 disposed between light source 210 and homogenizer 230.Optical relay 2310 can primarily be designed to, for example, transferlight from light source 210 to homogenizer 230. In such cases, one orboth of optical relay 2310 and homogenizer 230 may affect α₁, α₂, orboth. According to one aspect of the invention, one or both of opticalrelay 2310 and homogenizer 230 change α₁, but not α₂. In a preferredembodiment of the invention, α′₁, is equal to α₁, and α′₂ is equal toα₂. Optical relay 2310 may have different magnification factors alongthe x- and y-directions. In one particular embodiment of the invention,optical relay 2310 forms an image of output face 2305 of light source210 onto input face 230A of homogenizer 230. As such, output face 2305and input face 230A form an object-image relation relative to opticalrelay 2310. In a preferred embodiment of the invention, optical relay2310 has equal magnification factors along the x- and y-directions. Inanother preferred embodiment of the invention, the magnification factorof optical relay 2310 along both x- and y-directions is substantiallyequal to 1.

Homogenizer 230 can have any three-dimensional shape, for example, apolyhedron, such as a hexahedron. Homogenizer 230 can be solid orhollow. Homogenizer 230 may homogenize an input light by any suitableoptical method such as reflection, total internal reflection,refraction, scattering, or diffraction, or any combination thereof, orany other suitable method that may be used to homogenize an input light.

Optical transmittance of Homogenizer 230 is preferably no less than 50%,more preferably no less than 70%, and even more preferably no less than80%, where optical transmittance is the ratio of total light intensityexiting output surface 230B to total light intensity incident on inputface 230A.

Referring back to FIG. 2, mask 250 receives each of the transmittedhomogenized light segments and patterns each segment into a row of ndiscrete light subsegments along the y-direction, where n can be greaterthan one. As such, the light output of mask 250 is a mask patternedlight beam 255 which includes multiple light rows (three in FIG. 2),each light row having multiple light subsegments (again, three in FIG.2). According to the present invention, n is preferably greater than 10,more preferably greater than 20, even more preferably greater than 30,and even more preferably greater than 50. In the exemplary embodimentshown in FIG. 2, mask 250 patterns light segment 231A into three lightsubsegments 251A-1, 251A-2, and 251A-3, the three subsegments forminglight row 255-1; light segment 231B into three light subsegments 251B-1,251B-2, and 251B-3, the three subsegments forming light row 255-2; andlight segment 231C into three light subsegments 251C-1, 251C-2, and251C-3, the three subsegments forming light row 255-3. Therefore, in theexemplary embodiment shown in FIG. 2, n is equal to 3. Each discretelight subsegment can have any cross section, such as a rectangularcross-section, in which case, each subsegment has a length along they-direction and a width along the x-direction. FIG. 7 shows across-section of light subsegments 251A-1, 251A-2, and 251A-3 in thexy-plane. Light subsegment 251A-1 has a length L₁ and a width W₁, lightsubsegment 251A-2 has a length L₂ and a width W₂, and light subsegment251A-3 has a length L₃ and a width W₃. In general, mask 250 is capableof setting the length of each discrete light subsegment at any valuelimited, in general, by the length of a received correspondinghomogenized light segment.

Mask 250 can be any type of a mask that may be suitable for patterningan incident light. For example, mask 250 may include a shadow maskhaving a plurality of holes in, for example, a thin opticallynon-transmissive plate. Mask 250 may include diffractive elements usingoptical diffraction to pattern an incident light. Mask 250 may include alight valve or a Spatial Light Modulator (SLM), such as aliquid-crystal-based SLM, or a switchable mirror SLM. Mask 250 mayinclude a digital micromirror device, or a micro-electromechanicalsystem, such as a grating light valve. Mask 250 may include an opticalmask having fixed or permanent patterns that are either substantiallyoptically transparent or non-transmissive at a wavelength of interest.Exemplary methods that can be used to fabricate an optical mask include,photolithography, electron-beam lithography, printing, or any othermethod that may be used to generate a fixed pattern having opticallyclear and non-transmissive areas.

According to one particular embodiment of the invention, mask 250 iscapable of setting the length of each discrete light subsegment at anyvalue in a range from about 0.2 to about 2500 microns with an accuracyof about 0.1 microns or better, more preferably in a range from about 1to about 500 microns with an accuracy of about 0.1 microns or better,even more preferably in a range from about 10 to about 300 microns withan accuracy of about 1 micron or better, and still even more preferablyin a range from about 50 to about 150 microns with an accuracy of about1 micron or better. In general, by an accuracy of δ, it is meant thatmask 250 is capable of setting a length of a subsegment to L±δ microns,where L is any length value in a given preferred range. For example, byan accuracy of 1 micron, it is meant that mask 250 is capable of settinga length of a subsegment to L±1 microns, where L is any length value ina preferred range, such as from about 10 microns to about 300 microns,or from about 50 microns to about 150 microns.

According to one embodiment of the invention, for a length L_(a), whereL_(a) is any value in a range from about 50 microns to about 3000microns, mask 250 is capable of being designed to set the length of eachdiscrete light subsegment at any value in a range from about 0.9L_(a) toabout 1.1L_(a) with an accuracy of about 0.1 microns or better.According to another embodiment of the invention, for a length L_(a),where L_(a) is any value in a range from about 5 microns to about 500microns, mask 250 is capable of being designed to set the length of eachdiscrete light subsegment at any value in a range from about 0.8L_(a) toabout 1.2L_(a) with an accuracy of about 0.1 microns or better.

Referring back to FIG. 7, separation between light subsegments 251A-1and 251A-2 is d₁, and separation between light subsegments 251A-3 and251A-2 is d₂. In general, a separation between adjacent discrete lightsubsegments can be any value desirable in an application. According toone embodiment of the invention, mask 250 is capable of being designedto set the separation between any two adjacent discrete lightsubsegments at 0.1 microns or larger.

In one particular embodiment of the invention, all light subsegmentshave substantially the same length and are substantially equally spaced.Furthermore, the spacing between adjacent light subsegments issubstantially twice as long as the length of each light subsegment.

Referring back to FIG. 2, lens system 260 projects mask patterned lightbeam 255 onto substrate 270. As such, lens system 260 projects eachlight row of n discrete light subsegments (such as light row 255-1) ontosubstrate 270.

Furthermore, lens system 260 projects each of light rows 255-1, 255-2,and 255-3 onto substrate 270 such that the corresponding subsegmentsfrom each row (that is, subsegments forming a column in patterned lightbeam 255) substantially coincide on substrate 270. For example, lenssystem 260 projects light subsegments 251A-1, 251B-1, and 251C-1 ontosubstrate 270 so as to form a single projected light segment 270A.Similarly, lens system 260 projects light subsegments 251A-2, 251B-2,and 251C-2 onto substrate 270 so as to form a single projected lightsegment 270B. As yet another example, lens system 260 projects lightsubsegments 251A-3, 251B-3, and 251C-3 onto substrate 270 so as to forma single projected light segment 270C. Therefore, lens system 260 formsa single row of n discrete projected light segments along they-direction on substrate 270.

In a preferred embodiment of the invention, the distance between thefirst and the nth, that is, the last discrete projected light segments,is at least 5 millimeters, more preferably at least 10 millimeters, evenmore preferably at least 15 millimeters, and still even more preferablyat least 20 mm.

According to one embodiment of the invention, mask patterned light beam255 includes a two-dimensional array of discrete light subsegments,where the array has n columns and m rows. The m rows are divided into pgroups, each group including at least two rows of discrete lightsubsegments, where no row is included in more than one group.Furthermore, lens system 260 projects the m by n array of discrete lightsubsegments onto substrate 270 by superposing all the rows in each groupso as to form an array of projected light segments, where the array hasn columns and p rows. In the case where p is 1, all the m rows inpatterned light beam 255 are superposed forming a row of n projectedlight segments.

Such an array of projected light segments can be used to, for example,transfer a same-size array of a transferable material from a carrieronto substrate 270. Hence, the present invention can be used tosimultaneously pattern an array of pixels in a display component.Furthermore, the array of projected light segments can be used topattern the pixels in an entire display component by, for example, usinga step-and-repeat process.

The superposition or overlap of corresponding subsegments projected ontosubstrate 270 is further described in reference to FIG. 8 which shows aschematic side-view of a portion of imaging system 200 from FIG. 2. Inparticular, FIG. 8 shows mask 250, lens system 260, and substrate 270.FIG. 8 further shows light subsegments 251A-1, 251B-1, and 251C-1 asoutput of mask 250 and propagating along the z-direction. FIG. 8 furthershows projected light segment 270A onto substrate 270. According to oneparticular embodiment of the invention, lens system 260 projects,relays, or transfers light subsegments 251A-1, 251B-1, and 251C-1 ontosubstrate 270 in such a way that the transferred light subsegmentscoincide on substrate 270, thereby forming a single projected lightsegment 270A.

An advantage of superposition of corresponding light subsegments ontosubstrate 270 is increased light intensity for each projected lightsegment. As a result, each projected light segment, such as segment270A, can be capable of inducing a transfer of a transferable materialin a shorter amount of time, thereby increasing overall throughput.

In the invention, projection of light from a first plane to a secondplane refers to a transfer of light from the first plane to the secondplane. As such, the second plane need not lie in an image plane of thefirst plane. In particular, referring to FIG. 2, exit surface 252 ofmask 250 and front surface 271 of substrate 270 do not, in general, forman object-image relation relative to lens system 260. In other words,lens system 260 need not necessarily image surface 252 onto surface 271.

In one particular embodiment of the invention, lens system 260 imagessurface 252 onto surface 271 along the y-direction, but not along thex-direction. As such, while lens system 260 projects output light frommask 250 (that is, patterned light beam 255) onto substrate 270 alongboth the x- and y-directions, the lens system images the output lightonto substrate 270 along the y-direction, but not along the x-direction.Therefore, lens system 260 can have a magnification factor as betweenmask 250 and substrate 270 along the y-axis, and a projection scalefactor between the two along the x-axis. Referring back to FIG. 8, lightsubsegment 251A-1 has a length L₁ along the y-axis and a height W₁ alongthe x-axis. Similarly, projected light segment 270A has a length L_(o)along the y-axis and a height W_(o) along the x-axis. As such, lenssystem 260 has a magnification factor of L_(o)/L₁ and a projection scalefactor of W_(o)/W₁.

According to a preferred embodiment of the invention, the magnificationfactor of lens system 260 as between mask 250 and substrate 270 is lessthan 5, more preferably less than 3, and even more preferably less than2. In another preferred embodiment of the invention, the magnificationfactor is in a range from about 0.8 to about 1.2, more preferably in arange from about 0.9 to about 1.1, and even more preferably in a rangefrom about 0.95 to about 1.05. In still another preferred embodiment ofthe invention, the magnification factor is substantially equal to one.

Furthermore, the projection scale factor of lens system 260 as betweenmask 250 and substrate 270 is preferably in a range from about 0.02 toabout 1, more preferably in a range from about 0.04 to about 0.2, evenmore preferably in a range from about 0.05 to about 0.2, and even morepreferably in a range from about 0.06 to about 0.1.

In a preferred embodiment of the invention, lens system 260 is ananamorphic lens system having a magnification factor of about 1 alongthe y-axis and a projection scale factor in a range from about 0.06 toabout 0.1.

Referring back to FIG. 8, a projected light segment, such as lightsegment 270A, can have any intensity profile along x- and y-directions.Furthermore light segment 270A can have different intensity profilesalong different directions. According to one embodiment of theinvention, a projected light segment has a substantially uniformintensity profile, or a flat-top intensity profile, along the y-axis,and a Gaussian intensity profile along the x-axis. According to anotherembodiment of the invention, a projected light segment has asubstantially uniform intensity profile along both the x- andy-directions.

According to the present invention, when a donor film that includes atransferable material coated on a carrier, is placed in contact or nearcontact with substrate 270 between lens system 260 and substrate 270,each of the n discrete projected light segments (such as segments 270A,270B, and 270C in FIG. 2) is capable of inducing a transfer of thetransferable material from the carrier onto substrate 270. Such atransfer of material is further described in reference to FIGS. 9 and10.

FIG. 9 shows a schematic side-view of a portion of an imaging systemaccording to the present invention illustrating an example of a transferof a transferable material from a donor film onto a substrate. Inparticular, FIG. 9 shows substrate 270 placed on an optional stage 280,where stage 280 can be capable of being moved, in a predetermined way,along one or more directions, such as x-, y-, and z-directions, wherethe x-direction in FIG. 9 is perpendicular to the plane of the page asdenoted by a circle with a dot at its center. FIG. 9 further shows atransfer film 905 that includes a donor film 910 coated on a carrier 920with the donor film facing substrate 270. Donor film 910 includes atransferable material. Examples of transferable materials and donorfilms including same have previously been described in, for example,U.S. Pat. Nos. 5,747,217; 5,935,758; 6,114,088; 6,194,119; 5,521,035;5,766,827; 5,308,737; 5,725,989; and 5,998,085.

FIG. 9 shows a gap “R” between donor film 910 and substrate 270. Ingeneral, R can be quite small, in which case, donor film 910 can be incontact or close to contact with substrate 270. R can be made small by,for example, applying pressure to the top side of carrier 920. Asanother example, gap R can be reduced by applying a vacuum to the gaparea. FIG. 9 further shows projected light segments 270A, 270B, and 270Con substrate 270. These projected light segments are formed on substrate270 by lens system 260. Beam trajectories 930A, 930B, and 930C showexemplary light projection paths from lens system 260 to projected lightsegments 270A, 270B, and 270C, respectively. Each projected lightsegment is capable of transferring donor film 910 at an area of film 910that is illuminated by the projected light segment. For example,projected light segment 270B is capable of transferring portion 920B ofdonor film 910, where portion 920B corresponds to a portion of donorfilm 910 illuminated by projected light segment 270B. Similarly,projected light segments 270A and 270C are capable of transferringportions 920A and 920C of donor film 920, respectively. A result of sucha transfer is schematically shown in FIG. 10 where portions 920A, 920B,and 920C of donor film 910 have been transferred from carrier 920 ontosubstrate 270. In general, a transferred portion of donor film 920 mayor may not have the same shape or size as a corresponding illuminatedportion of the film. In one embodiment of the invention, the size of atransferred area is within 30%, more preferably within 20%, even morepreferably within 10% of the size of a corresponding illuminated area ofdonor film 910. In another embodiment of the invention, the size andshape of a transferred portion of donor film 920 are substantially thesame as those of the corresponding illuminated area.

Transfer film 905 may include additional layers or films not shown inFIG. 9, such as a light-to-heat conversion film. Examples of variouslayers that may be included in transfer film 905 have been previouslydisclosed, for example, in U.S. Pat. Nos. 5,521,035; 6,114,088;5,725,989; 6,194,119; and 5,695,907.

Referring back to FIG. 2, a shutter may be disposed at one or morelocations along the beam path from light source 210 to substrate 270 toturn “on” or “off” the projected lights segments on substrate 270. Anexample of one such shutter is schematically shown in FIG. 9, where ashutter 940 is placed between lens system 260 and substrate 270. Assuch, when shutter 940 is open, projected light segments 270A, 270B, and270C are formed on substrate 270 and are capable of transferringportions of donor film 910. Similarly, when shutter 940 is closed, nolight can reach substrate 270 and, thus, there is no induced transfer ofdonor film 910. Where stage 280 is moved along a particular path in thexy-plane, a projected light segment, such as projected light segment270A, can induce a transfer in a shape or form that closely follows thepath taken by stage 280. For example, if stage 280 is moved along x-axiswhile projected light segments 270A, 270B, and 270C are all on, then theprojected light segments can transfer donor film 910 onto substrate 270in a form of three lines along the x-axis. On the other hand, if, forexample, stage 280 is stationary, then the transferred areas cancorrespond closely to the size of the projected light segments.Accordingly, an imaging system according to one embodiment of theinvention can be used to transfer a transferable material in apre-determined form such as discrete pixels corresponding to pixels in adisplay, or parallel lines, for example, covering corresponding columnsin a display, or any other shape or form that may be desirable whenpatterning a display component in a particular application.

Total light output power of light source 250 is preferably sufficientlyhigh so that projected light segments 270A, 270B, and 270C are capableof inducing a transfer of a transferable material from a donor film tosubstrate 270. In one embodiment of the invention total output power oflight source 250 is at least 200 watts, more preferably at least 400watts, even more preferably at least 600 watts, even more preferably atleast 800 watts, and still even more preferably at least 900 watts.Furthermore, light output of light source 250 may be pulsed orcontinuous.

In one embodiment of the invention, total light power delivered tosubstrate 270 is at least 50 watts, more preferably at least 100 watts,even more preferably at least 150 watts, and even more preferably atleast 200 watts.

Referring back to FIG. 2, according to one embodiment of the invention,mask 250 is capable of patterning each homogenized light segment (suchas segment 231A) into a row of discrete light subsegments (such assubsegments 251A-1, 251A-2, and 251A-3), where the length of eachsubsegment can be set with a high degree of accuracy. A few exemplaryembodiments of mask 250 are now described.

FIG. 11 illustrates a schematic top-view of a mask 1100 as a particularembodiment of mask 250. Mask 1100 includes multiple opticallytransmissive areas or parts in an otherwise optically non-transmissiveregion. In particular, exemplary mask 1100 has three opticallytransmissive areas 1130A, 1130B, and 1130C surrounded by opticallynon-transmissive area 1110. According to one aspect of the invention,each transmissive part is centered along an axis. For example, opticallytransmissive part 1130C is centered on axis 1143C. Furthermore,according to one embodiment of the invention, axis 1143C is orientedalong the x-axis.

By optically non-transmissive it is meant that any light that may betransmitted by area 1110 has a sufficiently low light power or intensityas to be incapable of inducing a transfer of a transferable materialfrom a donor film onto substrate 270. In one embodiment of theinvention, total optical transmission of areas 1110 is preferably lessthan 30%, more preferably less than 20%, even more preferably less than10%, and even more preferably less than 5%. Area 1110 can be opticallynon-transmissive by being optically reflective, absorptive, diffractive,or a combination thereof. Area 1110 can be optically reflective by, forexample, including a reflective metal coating. Exemplary metal materialsthat can be used in a reflective metal coating include silver, gold,chromium, aluminum, copper, or a combination thereof, or any othersuitable reflective metal material. Generally, all metals have someresidual optical absorption. As such, a high intensity light incident onmask 1100 can generate a substantial amount of heat in the reflectivemetal layer, and therefore, in mask 1100. The generated heat can notonly damage the metal coating, but it can also cause thermal expansion,even non-uniform thermal expansion, in the mask, thereby introducingsignificant changes in the intended dimensions of various features inthe mask.

As another example, area 1110 can be optically reflective by including amultilayer dielectric coating that reflects light at a wavelength ofinterest by optical interference. In such a case, one or more layers inthe multilayer dielectric coating can, for example, be quarter wavethick at the wavelength of interest.

As another example, area 1110 can be optically reflective by including areflective multilayer dielectric coating disposed on a reflective metallayer. In this example, the multilayer dielectric coating can reflect asignificant portion of an incident light with essentially no or verylittle optical absorption. Any residual light that may be transmitted bythe multilayer dielectric coating is reflected by the metal layer. Anadvantage of such a construction is that the metal is not directlyexposed to high intensity incident light that can cause damage to orgenerate an unacceptable amount of heat in the metal layer.

Area 1110 may be designed so that any light that may be reflected bythis area is reflected in an off-axis direction, that is, in a directionsufficiently different from the light incidence direction so as to avoidother elements in imaging system 200.

For simplicity and without loss of generality, it is assumed that thethree optically clear or transmissive areas 1130A, 1130B, and 1130C havethe same shape and dimensions. In particular, each of the clear areas isa trapezoid having a length L₄ for the lower base (corresponding to alocation X₁ along the x-axis), a length L₅ for the upper base(corresponding to a location X₂ along the x-axis), and a height W₄(corresponding to the distance between X₁ and X₂). FIG. 11 also showshomogenized light segment 231A (from FIG. 2) incident on mask 1100 atlocation X_(o) along the x-axis. It can be appreciated that mask 1100patterns homogenized light segment 231A into three light subsegments251A-1, 251A-2, and 251A-3 corresponding to clear areas 1120A, 1120B,and 1120C, respectively, where the length of each subsegment (see FIG.7) is L′₄, the length of each trapezoid at X_(o), the location of lightincidence. A key characteristic of mask 1100 according to one particularembodiment of the invention, is that the length of each light subsegment(such as subsegment 251A-1) can essentially be set at any value in arange from about L₄ to about L₅ by choosing an appropriate locationalong the x-axis.

Mask 1100 can be made using any or a combination of commerciallyavailable patterning methods or any patterning technique that may besuitable in making the mask. Exemplary patterning methods includephotolithography, ink jet printing, laser ablation, photo-bleaching,electron-beam lithography, machining, ion milling, reactive ion etching,or the like. One or more of said exemplary patterning methods is capableof patterning masks as large as, for example, 25 cm by 25 cm overessentially the entire area of the mask with features smaller than onemicron and larger than, for example, 100 microns with a dimensionalaccuracy of 1 micron or even 0.1 microns or better.

Referring back to FIG. 11, an “active area” can be defined for mask1100, where the active area is defined by a smallest outer perimeterthat includes all the optically clear features in the mask that are usedto pattern an incident beam. For example, for mask 1100 a rectangularactive area can be defined with a length L₆ along the y-axis and a widthW₄ along the x-axis. Dimensions W₄ and L₆ can assume any value accordingto a particular application in which mask 1100 is used. In particular,according to the present invention, the active area of mask 1100 cancover any area in arrange from about 5 mm by 5 mm to about 40 cm by 40cm.

FIG. 11 shows a mask pattern where the length (the dimension along they-axis) of each clear aperture (such as area 1130C) essentially variescontinuously between L₄ and L₅. FIG. 12 illustrates a schematic top-viewof a mask 1200 as another embodiment of mask 250, where the length ofeach clear aperture changes in discrete steps at several points alongthe x-axis. Similar to mask 1100, mask 1200 includes three opticallytransmissive areas 1230A, 1230B, and 1230C surrounded by opticallynon-transmissive area 1210, where area 1210 can be made opticallynon-transmissive similar to area 1110 in mask 1100.

Similar to mask 1100, for simplicity and without loss of generality, itis assumed that the three optically clear areas 1230A, 1230B, and 1230Chave the same shape and dimensions. In particular, each of the clearareas includes three segments, each segment having a constant length.For example, optically transmissive area 1230C has a bottom clearsegment having a constant length L₇, a middle clear segment having aconstant length L₈, and a top clear segment having a constant length L₉.As such, the length of optically clear area 1230C makes a step change atX₄ and another step change at X₅. Furthermore, optically transmissivearea 1230C has a height W₅ which is the distance between coordinates X₃and X₇. FIG. 12 also shows homogenized light segment 231A incident onmask 1200 at location X₆ along the x-axis. Therefore, in the example ofFIG. 12, mask 1200 patterns homogenized light segment 231A into threelight subsegments 251A-1, 251A-2, and 251A-3 corresponding to clearareas 1220A, 1220B, and 1220C, respectively, where the length of eachsubsegment is L₉. An advantage of mask 1200 is that a small change inlocation of incident light (that is, a small change in X₆) does notaffect the length of each patterned light subsegment. At the same time,the length of each light subsegment can be one of a discrete number ofvalues, in this case, one of three values L₇, L₈, and L₉ by, forexample, moving one or both of an incident light and mask 1200.

Similar to mask 1100, a rectangular “active area” can be defined formask 1200 having a length L₁₀ along the y-axis and a width W₅ along thex-axis.

FIG. 13 illustrates a schematic top-view of a mask 1300 as anotherembodiment of mask 250, where the length of each clear aperture is aconstant along the x-axis. Similar to mask 1100, mask 1300 includesmultiple, such as three optically transmissive areas 1330A, 1330B, and1330C surrounded by optically non-transmissive area 1310, where area1310 can be made optically non-transmissive similar to area 1110 in mask1100.

Similar to mask 1100, for simplicity and without loss of generality, itis assumed that the three optically clear areas 1330A, 1330B, and 1330Chave the same shape and dimensions. In particular, each of the clearareas has a rectangular shape having a constant length L₁₁ and a heightW₆. Homogenized light segment 231A incident on mask 1300 at any locationX₁₀ between locations X₈ and X₉ results in a patterning of thehomogenized light segment into three light subsegments 251A-1, 251A-2,and 251A-3 corresponding to clear areas 1320A, 1320B, and 1320C,respectively, where the length of each subsegment is L₁₁. An advantageof mask 1300 is that even a large change in location of incident light(that is, a large change in X₁₀) does not affect L₁₁, the length of eachpatterned light subsegment.

Similar to mask 1100, a rectangular “active area” can be defined formask 1300 having a length L₁₂ along the y-axis and a height W₆ along thex-axis.

In each of the exemplary embodiments of mask 250 described in FIGS. 11through 13, the embodiment includes three distinct optically clearareas, thereby each embodiment is capable of patterning an incidenthomogenized light segment into three light subsegments. According to thepresent invention, M, the number of distinct optically clear areas inmask 250 is preferably greater than 10, more preferably greater than 20,even more preferably greater than 30, and even more preferably greaterthan 50.

Total optical transmittance (at a wavelength of interest), and inparticular, specular optical transmittance (again, at a wavelength ofinterest) of an optically transmissive area, such as, for example, area1130A in FIG. 11, area 1230B in FIG. 12, and area 1320C in FIG. 13, isquite uniform within the entire region of the optically clear area.According to one aspect of the invention, uniformity of total opticaltransmittance within the entire region of an optically transmissive areaof a mask according to any embodiment of the invention is 1% or better,more preferably 10⁻²% or better, even more preferably 10⁻³% or better,even more preferably 10⁻⁴% or better, and still even more preferably10⁻⁵% or better, where by an optical uniformity of, for example, 10⁻⁴%or better it is meant that the percent difference between total opticaltransmittance at any two points within an optically transmissive area is10⁻⁴ or less.

Furthermore, an internal optical transmittance may be defined for anylocation within an optically transmissive area of a mask as the totaloptical transmittance (at a wavelength of interest) excluding allinterfacial (or Fresnel) reflection losses, if any. The internal opticaltransmittance of a mask, according to any embodiment of the invention,at any point within an optically transmissive area of the mask is atleast 99%, more preferably at least 99.9%, even more preferably at least99.99% and even more preferably at least 99.999%.

In one embodiment of the invention, mask 250 is capable of patterning anincident light beam with great efficiency, meaning with no or littleoverall optical loss. As such, mask 250 can be capable of patterning anincident light beam without rejecting a substantial portion of theincident light. For example, imaging system 200 can include a lightrecycling mechanism in order to pattern an incident light whilemaintaining high overall optical transmission. As another example,imaging system 200 can include an optical apparatus for directing mostor essentially all of an incident light to the optically transmissiveparts of mask 250. For example, an array of microlenses, such ascylindrical microlenses, can be used to direct an incident light todifferent optically transmissive parts of mask 250. An example of anoptical apparatus for redirecting an incident light to clear parts ofmask 250 may be found in U.S. Pat. No. 6,366,339.

According to one embodiment of the invention, imaging system 200 hashigh overall optical transmission, where overall optical transmissionrefers to the ratio of the total amount of light delivered to substrate270 to the total light output of light source 210. According to oneembodiment of the invention, the overall optical transmission of imagingsystem 200 is at least 20%, more preferably at least 30%, morepreferably at least 40%, and even more preferably at least 50%.According to another embodiment of the invention, the overall opticaltransmission of imaging system 200 is at least 70% and more preferablyat least 80%.

A mask according to any embodiment of the present invention may includea main mask and one or more pre-masks, where the pre-masks can beprimarily designed to protect the optically non-transmissive areas ofthe main mask from damage that can be caused, for example, by a highintensity incident light beam. Furthermore, each optically transmissivearea in the main mask has a corresponding optically transmissive areasin the one or more pre-masks. In addition, the opening or the opticalaperture provided by an optically transmissive area in a pre-mask islarger than the opening or the optical aperture provided by thecorresponding optically transmissive area in the main mask. As such, aperimeter of an optically clear area in a pre-mask lies without aperimeter of a corresponding clear area in the main mask. FIG. 14illustrates a schematic side-view of a portion of a mask 1400 accordingto one embodiment of the invention, where the mask includes a pre-mask.In particular, optical mask 1400 includes a main mask 1410 and apre-mask 1420 disposed proximate main mask 1410. Main mask 1410 includesoptically non-transmissive areas 1430A, 1430B, and 1430C, and opticallytransmissive areas 1440A and 1440B. Similarly, pre-mask 1420 includesoptically non-transmissive areas 1430A′, 1430B′, and 1430C′, andoptically transmissive areas 1440A′ and 1440B′. Optically transmissiveareas 1440A and 1440B have lengths L₁₃ and L₁₄, respectively. Similarly,optically transmissive areas 1440A′ and 1440B′ have lengths L′₁₃ andL′₁₄, respectively. It can be seen from FIG. 14 that L′₁₃ is larger thanL₁₃ and L′₁₄ is larger than L₁₄. As such, the optical aperture providedby, for example, clear area 1440A′ is larger than the optical apertureprovided by the corresponding clear area 1440A. An advantage of pre-mask1420 having larger optically clear areas than their correspondingoptically clear areas in the main mask is ease of alignment between thepre-mask and main mask. A further advantage is that an inadvertent smallmove by the mask or the pre-mask, or any thermal expansion in pre-mask1420, does not change the linewidth of a light subsegment (such as lightsubsegment 251A-1 in FIG. 2).

Referring back to FIG. 11, the intensity of incident homogenized lightsegment 231A may be sufficiently high that a residual optical absorptionin the optically non-transmissive area 1110 (and to a lesser extent, inthe optically transmissive areas) may cause mask 1100 to thermallyexpand. A thermal expansion in the mask may cause dimensions of thefeatures in the mask, such as length L′₄, to change beyond an acceptablevalue, for example, because the expansion would cause an unacceptablemisregistration between projected light segments (for example, lightsegments 270A, 270B, and 270C in FIG. 2) and a display component that isbeing patterned. Providing one or more pre-masks can mitigate theundesirable effects of thermal expansion in the main mask. Analternative or additional approach is to provide a cooling mechanism forthe mask to compensate for undesirable thermal effects caused by, forexample, residual light absorption. Cooling can be provided for example,by passing a stream of cool air over the mask. Another example isillustrated in FIG. 15 showing a schematic side-view of a mask assembly1500 which includes a mask 1505 enclosed in a cooling chamber 1510.Cooling chamber 1510 contains a coolant 1540 for removing heat generatedin mask 1505. Cooling chamber 1510 has optional inlet 1520 and outlet1530 for letting coolant 1540 in and out of cooling chamber 1510. Thecooling mechanism displayed in FIG. 15 may be part of an open- orclosed-loop cooling system. Coolant 1540 may be a gas, such as air, orchemically inert gases such as argon or nitrogen. Coolant 1540 may be aliquid, such as water, or a modified water solution. Cooling chamber1510 further includes optically transmissive input window 1511 andoutput window 1512 for providing passage for an incident light beam.

In some applications, it may be desirable or necessary to maintain atleast some components or portions of an imaging system of the inventionat a relatively constant temperature. In some applications, it may bedesirable or necessary to maintain the entire imaging system includingall the optical elements and mounts that hold the elements in place, ata relatively constant temperature. A relatively constant temperature maybe required, for example, to maintain accurate registration duringpatterning a display component. As such, elements not directly a part ofthe imaging system, such the display component or donor films may needto be maintained at a constant temperature also. Maintaining a constantoverall temperature may be achieved, for example, by providing adedicated temperature control system for each element or sub-assembly ofthe imaging system. The temperature may further be maintained at arelatively constant value by placing the entire imaging system in atemperature controlled housing such as a temperature controlled room.

Referring back to FIG. 2, light source 210 is capable of emitting apatterned light beam 215. In what follows different embodiments of lightsource 210 are discussed in some detail. FIG. 16 illustrates a schematicthree-dimensional view of a light bar assembly 1600 in accordance to oneparticular embodiment of the invention. In one embodiment of theinvention, light source 250 includes one or more light bar assemblies1600. Light bar assembly 1600 includes a light bar 1610 and acollimating lens assembly 1630. Light bar 1610 includes a plurality ofdiscrete light emitters 1620. For example, FIG. 16 shows four such lightemitters.

Light emitters 1620 are capable of emitting light at one or morediscrete wavelengths of interest, one or more continuous ranges ofwavelength, or a combination thereof. Furthermore, light emitters 1620may emit light in any range of the electromagnetic spectrum, such as theultraviolet range, the near ultraviolet range, the visible range, thenear infrared range, or the infrared range, or any combination thereof.In one particular embodiment of the invention, each light emitter 1620emits light at one or more wavelengths in a range from about 700nanometers to about 1700 nm, more preferably in a range from about 750nanometers to about 1200 nm, even more preferably in a range from about750 nanometers to about 900 nm, even more preferably in a range fromabout 770 nanometers to about 830 nm, and still even more preferably ina range from about 780 nanometers to about 820 nm.

In general, light emitters 1620 can emit light having anycross-sectional profile. For example, each of light emitters 1620 shownin FIG. 16 emit light having a rectangular profile, where therectangular profile at the output face 1612 of light bar 1610 has alength l_(e) along the y-axis and a height W_(e) along the x-axis. Otherexemplary profiles include a circle, an ellipse, a polygon, such as aquadrilateral, a rhombus, a parallelogram, a trapezoid, a rectangle, asquare, or a triangle. Furthermore, the size and dimensions of lightemitted by light emitter 1620 may vary depending on such parameters asavailability, design of the overall imaging system, and the particularapplication of interest. In one particular embodiment of the invention,light emitter 1620 emits light preferably having a polygon profile, morepreferably a quadrilateral profile, and even more preferably arectangular profile.

Furthermore, according to one particular embodiment of the invention,light emitter 1620 emits light having a rectangular profile, wherepreferably l_(e) is in a range from about 25 to about 400 microns andw_(e) is in a range from about 0.1 to about 10 microns, more preferablyl_(e) is in a range from about 50 to about 300 microns and w_(e) is in arange from about 0.3 to about 5 microns, and even more preferably l_(e)is in a range from about 75 to about 225 microns and w_(e) is in a rangefrom about 0.5 to about 3 microns. Furthermore, s_(e), separationbetween adjacent light emitters 1620, is preferably in a range fromabout 25 microns to about 400 microns, more preferably in a range fromabout 50 microns to about 300 microns, and even more preferably in arange from about 75 microns to about 225 microns.

Light emitted by light emitters 1620 and before going throughcollimating lens assembly 1630 has a full divergence angle α″₁ along they-axis and a full divergence angle α″₂ along the x-axis, where α″₁ cantypically be in a range from about 2 degrees to about 15 degrees, andα″₂ can typically be in a range from about 5 degrees to about 50degrees.

For simplicity, ease of illustration, and without loss of generality,FIG. 16 shows a physical separation between collimating lens assembly1630 and output face 1612 of light bar 1610. In most applications,however, it may be desirable that collimating lens assembly 1630 beattached, for example, by an optical adhesive, to output face 1612 oflight bar 1610. In some applications, an optically transmissive materialsuch as an index matching material may be fill the gap betweencollimating lens assembly 1630 and light bar 1610, for example, toreduce reflection losses.

Collimating lens assembly 1630 may be designed to reduce divergenceangles α″₁ and α″₂. In one embodiment of the invention, collimating lensassembly 1630 substantially reduces divergence angle α″₂ withoutsignificantly affecting α″₁ . As such, collimating lens assembly 1630can act like a cylindrical lens, although it may include multiplelenses, with its direction of optical power oriented along the x-axis asshown in FIG. 16. According to this embodiment of the invention,collimating lens assembly 1630 substantially collimates output light ofeach light emitter 1620 along the x-direction. Light emitted by eachlight emitter 1620 and transmitted by collimating lens assembly has afull divergence angle α₂ along the x-axis and full divergence angle α₁along the y-axis, where α₁ can be substantially the same as α″₁. α₂ ispreferably not greater than 1 degree, more preferably not greater than0.5 degrees, even more preferably not greater than 0.1 degrees, and evenmore preferably not greater than 0.05 degrees, and still even morepreferably not greater than 0.03 degrees.

According to one aspect of the invention, a relatively large α″₁ (forexample, where α″₁ is at least 30 degrees) combined with a relativelysmall s_(e) (for example, where s_(e) is no greater than 225 microns),allow light emitted from light emitters 1620 to partially mix andoverlap in the yz-plane (along the y-axis) so that emitted light segment1611A, light output of collimated lens assembly 1630, appears to have acontinuous profile in the xy-plane. In particular, emitted light segment1611A has a uniformity profile along the y-axis which is similar toprofile 211A-y shown in FIG. 4A and a uniformity profile along thex-axis which is similar to profile 211A-x shown in FIG. 4B. Emittedlight segment 1611A can be one of the emitted light segments shown inFIG. 2, such as emitted light segment 211A.

A light bar assembly may include more than one light bar 1610, such as alight bar assembly shown in FIG. 17. FIG. 17 illustrates a schematicthree-dimensional view of a light bar assembly 1700 in accordance withanother embodiment of the invention. Light bar assembly 1700 includes astack of two discrete light bars 1710A and 1710B. Each of light bars1710A and 1710B includes a plurality of light emitters 1720A and 1720B,respectively. For example, FIG. 17 shows three light emitters in eachlight bar. Light bar assembly 1700 further includes a collimating lensassembly 1730. In general, each light bar requires its own dedicatedcollimating lens system to provide light collimation in one or moredirections. As such, collimating lens assembly 1730 includes twocollimating lens subassemblies 1730A and 1730B, one subassembly for eachlight bar. According to one aspect of the invention, each lenssubassembly substantially collimates light emitted by its correspondinglight bar in the x-direction but not in the y-direction. Collimatinglens subassemblies 1730A and 1730B may be separate parts formingcollimating lens assembly 1730, or they may be an integral part of thelens assembly.

According to one aspect of the invention, the output of collimating lensassembly 1730 includes emitted light segments 1711A and 1711B, eachhaving a rectangular profile and propagating along the z-axis. Inparticular, each of emitted light segment 1711A and 1711B has auniformity profile along the y-axis which is similar to profile 211A-yshown in FIG. 4A and a uniformity profile along the x-axis which issimilar to profile 211A-x shown in FIG. 4B. Emitted light segments 1711Aand 1711B can, for example, be two of the emitted light segments shownin FIG. 2, such as emitted light segments 211A and 211B.

FIG. 17 shows a two dimensional array of light emitters by stacking twodiscrete light bars 1710A and 1710B, each having a one-dimensional arrayof light emitters (1720A and 1720B, respectively). FIG. 18, on the otherhand, illustrates a light bar assembly 1800 that includes a monolithictwo-dimensional array of light emitters 1820 (e.g., a three by threearray as shown in FIG. 18) where light emitters 1820 can be similar tolight emitters 1620. In particular, light bar assembly 1800 includesthree rows 1840A, 1840B, and 1840C of light emitters 1820, each row oflight emitters including three light emitters. Light bar assembly 1800further includes a collimating lens assembly 1830 which includes threecollimating lens subassemblies 1830A, 1830B, and 1830C, each primarilydesigned to substantially collimate output light from a correspondingrow of light emitters in the x-direction but not in the y-direction.

According to one aspect of the invention, the output of collimating lensassembly 1830 includes emitted light segments 1811A, 1811B, and 1811C,each having a rectangular profile and propagating along the z-axis. Inparticular, each of emitted light segment 1811A, 1811B, and 1811C has auniformity profile along the y-axis which is similar to profile 211A-yshown in FIG. 4A and a uniformity profile along the x-axis which issimilar to profile 211A-x shown in FIG. 4B. Emitted light segments1811A, 1811B, and 1811C can, for example, be the three emitted lightsegments 211A, 211B, and 211C shown in FIG. 2.

Referring back to FIG. 2, according to one embodiment of the invention,patterned light beam 215 which includes a plurality of emitted lightsegments, can be formed by combining two or more sets of emitted lightsegments, where each set can be produced by, for example, a light barassembly such as those shown in FIGS. 16-18. FIG. 19 illustrates aschematic three-dimensional view of combining two sets of emitted lightsegments to form a new larger set of emitted light segments. Inparticular, FIG. 19 shows a first set of emitted light segments 1911-1and a second set of emitted light segments 1911-2, where each set ofemitted light segments can be the output of a light bar assembly such asthose shown in FIGS. 16-18. In the exemplary embodiment shown in FIG.19, first set of emitted light segments 1911-1 includes three emittedlight segments 1911B, 1911D, and 1911F where each emitted light segmentcan be similar to light segment 1611A described in reference to FIG. 16.Similarly, second set of emitted light segments 1911-2 includes threeemitted light segments 1911A, 1911C, and 1911E where each emitted lightsegment can be similar to light segment 1611A.

FIG. 19 further shows a light combiner 1950 having alternate areas ofhigh specular optical transmittance and reflectance. In particular,combiner 1950 has areas 1950A, 1950C, and 1950E each having a highspecular optical reflectance, and areas 1950B, 1950D, and 1950F eachhaving a high specular optical transmittance. Beam combiner 1950 isoriented in such a way that each optically transmissive area of the beamcombiner transmits a corresponding emitted light segment from the firstset of light segments, and each optically reflective area of the beamcombiner reflects a corresponding emitted light segment from the secondset of light segments, so that the transmitted and reflected emittedlight segments form a new larger set of emitted light segmentspropagating along a same direction without any mixing or partial overlapbetween the segments. For example, first set of light segments 1911-1can be propagating along the z-direction, having a cross-sectionalprofile in the xy-plane as shown in FIG. 20A. Furthermore, second set oflight segments 1911-2 can be propagating along the y-direction, having across-sectional profile in the xz-plane as shown in FIG. 20B. Lightcombiner 1950 can be oriented to lie in a plane normal to the yz-planeand making a 45 degree angle with the y- or z-axis. Furthermore, as canbe seen from FIGS. 20A and 20B, emitted light segments of the first setare positionally offset with respect to the emitted light segments ofthe second set along the x-axis. Furthermore, light combiner 1950 ispositioned so that emitted light segments 1911B, 1911D, and 1911F of thefirst set line up with transmissive areas 1950B, 1950D, and 1950F of thecombiner, and emitted light segments 1911A, 1911C, and 1911E of thesecond set line up with reflective areas 1950A, 1950C, and 1950E of thecombiner. As a result, beam combiner 1950 transmits emitted lightsegments 1911B, 1911D, and 1911F to form emitted light segments 1911B′,1911D′, and 1911F′, and reflects emitted light segments 1911A, 1911C,and 1911E to form emitted light segments 1911A′, 1911C′, and 1911E′ sothat the reflected and transmitted emitted light segments form apatterned light beam 1912 which includes emitted light segments 1911A′through 1911F′ propagating along the z-direction. In one aspect of theinvention there is little or no light mixing or partial overlap betweenthe emitted light segments along the x-axis. In another aspect of theinvention, there is some overlap between the emitted light segmentsalong the x-axis. In a preferred embodiment of the invention, any overlap between emitted light segments is at most partial, meaning that theoverlap is no more than about 50% between adjacent emitted lightsegments. Patterned light beam 1912 has a cross-sectional profile in thexy-plane as shown in FIG. 20C, and can, for example, be patterned lightbeam 215 shown in FIG. 2.

An advantage of combining sets of emitted light segments as shown inFIG. 19 is increased light power or intensity at substrate 270 (see FIG.2) resulting in increased overall throughput. It can be appreciated thatpatterned light beam 1912 may be combined with a similar patterned lightbeam using a light combiner similar to light combiner 1950 to form a newpatterned light beam with more emitted light segments and thus, evenmore light power or intensity at substrate 270. As such, the combiningmethod described in reference to FIG. 19 may be used to combine two ormore sets of emitted light segment to form a patterned light beam suchas patterned light beam 215 shown in FIG. 2.

According to one particular embodiment of the invention a light combiner1950 is used to combine a first set of emitted light segments having n′emitted light segments with a second set of emitted light segments alsohaving n′ emitted light segments, thereby forming a patterned light beamhaving 2 n′ emitted light segments where n′ is preferably at least 1,more preferably at least 2, even more preferably at least 3, and evenmore preferably at least 4. In one particular embodiment of theinvention, n′ is 8.

FIG. 21 illustrates a schematic top-view of a different method ofcombining two or more sets of emitted light segments to form a largerset of emitted light segments in accordance with another embodiment ofthe invention. In particular, FIG. 21 shows a first set of emitted lightsegments 2111-1 propagating along the y-direction, and a second set ofemitted light segments 2111-2 propagating along the z-direction. Lightin each set is polarized. For example, each set has a linearly orientedparallel polarization, meaning that the direction of polarization is inthe yz-plane as denoted by symbol 2102. FIG. 21 further shows a retarderelement 2110 placed in the path of set 2111-1 to change the direction ofpolarization from parallel to perpendicular, thereby forming a first set2111-1′ having a perpendicular polarization, where by perpendicularpolarization it is meant that the direction of polarization is along thex-axis (perpendicular to the yz-plane) as denoted by symbol 2101.

FIG. 21 further shows a polarizing beam combiner 2120 that uses thedifference between the parallel and perpendicular polarizations tocombine the first and the second sets. For example, FIG. 21 shows acubic polarizing beam combiner 2120 having an input face 2121 forreceiving light from the second set and an input face 2122 for receivinglight from the first set. Polarizing beam combiner 2120 has a hypotenuse2125 having a property of reflecting light having a perpendicularpolarization and transmitting light having a parallel transmission. Assuch, polarizing beam combiner 2120 combines light from the first setwith light from the second set by reflecting light from the first setand transmitting light from the second set, thereby forming a patternedlight beam 2115-1. Patterned light beam 2115-1 can, for example, bepatterned light beam 215 in FIG. 2.

Polarizing hypotenuse 2125 may be any polarizing element capable ofreflecting light having a first polarization and transmitting lighthaving a second polarization, where the first and second polarizationsare different. For example, polarizing hypotenuse 2125 may be amultilayer dielectric film as described, for example, in U.S. Pat. No.2,403,731. Polarizing hypotenuse 2125 may be a multilayer organicoptical film or a wire-grid polarizer previously described in, forexample, U.S. Pat. No. 6,486,997. In general, polarizing beam combiner2120 can be any polarization sensitive element capable of reflectinglight of one polarization and transmitting light of a differentpolarization.

In one embodiment of the invention, the emitted light segments of firstset 2111-1 are substantially aligned, along the x-axis, with the emittedlight segments of second set 2111-2 so that when combined by beamcombiner 2120, corresponding segments from the two sets substantiallyoverlap. In another embodiment of the invention, the emitted lightsegments of first set 2111-1 are offset, along the x-axis, relative tothe emitted light segments of second set 2111-2 so that when combined bybeam combiner 2120, the number of emitted light segments in patternedlight beam 2150 is the total number of emitted light segments in thefirst and second sets. Patterned light beam 2150 can, for example, bepatterned light beam 215 in FIG. 2.

If desirable, a polarizing beam combiner 2130, similar to polarizingbeam combiner 2120, can be used to combine light from a third set ofemitted light segments 2111-3 (going through retarder 2110′) with afourth set of emitted light segments 2111-4 to form a patterned lightbeam 2115-2, where patterned light beam 2115-2 can, for example, bepatterned light beam 215 in FIG. 2.

In one embodiment of the invention, a light combiner 2150, similar tolight combiner 1950 of FIG. 19, may be used to combine patterned lightbeams 2115-1 and 2115-2 to form a patterned light beam 2115-3.

FIG. 22 illustrates a light source 2210 in accordance with anotherembodiment of the invention. FIG. 22 also shows a portion of imagingsystem 200 for ease of illustration. Light source 2210 can, for example,be light source 210 shown in FIG. 2. Light source 2210 includesmultiple, for example, three light emitting devices 2220A, 2220B, and2220C. Each of the light emitting devices may, for example, be a lightguide source, such as a fiber light source. For example, each lightemitting device may be an optical fiber coupled to an output of a laser.As such, output light of light emitting devices 2220A, 2220B, and 2220Cmay be polarized.

Light source 2210 further includes light collimating lens assemblies2225A, 2225B, and 2225C for collimating or partially collimating theoutput light of the light emitting devices in one or more directions. Inaddition, the light collimating lens assemblies 2225A, 2225B, and 2225Cmay perform additional functionalities such as beam shaping, polarizing,retarding, or any other function that may be desirable to perform on theoutput of the light emitting devices.

Light source 2210 further includes a scanner 2230 that receives outputlight of each of the light emitting devices and scans each receivedlight output across mask 250. The exemplary scanner shown in FIG. 22 isa polygon-shaped mirror 2230 fast-rotating around PP′, a central axis ofthe mirror. Each side 2231 of polygon-shaped mirror 2230 has a highspecular optical reflection. As polygon-shaped mirror 2230 rotates, itforms a patterned light beam 2215 which includes emitted light segments2211A, 2211B, and 2211C. Patterned light beam 2215 can, for example, bepatterned light beam 215 of FIG. 2, in which case, emitted lightsegments 2211A, 2211B, and 2211C can be emitted light segments 211A,211B, and 211C. Emitted light segments 2211A, 2211B, and 221IC caneventually (for example, after going through a light homogenizer 230) bereceived and patterned by mask 250.

Other types of light scanners can be used to scan light output of lightemitting devices 2220A, 2220B, and 2220C. Exemplary light scannersinclude galvanometer mirrors (broadband or resonant), holographicscanners, electro-optic scanners, acousto-optic scanners,opto-mechanical scanners, or any other scanning method that may besuitable for forming discrete emitted light segments.

According to one embodiment of the invention, two or more imagingsystems can be used to simultaneously pattern a display component,where, for example, each imaging system patterns a different area of thedisplay component.

Referring back to FIG. 9, after processing a transfer film 905 bytransferring sufficient portions of donor film 910, a processed transferfilm 905 may be replaced with an unprocessed transfer film 905 tocontinue the transfer process. A replacement may be achieved by removinga discrete sheet of a processed transfer film 905 and placing anunprocessed transfer film 905 in its place. As such, patterning adisplay component may be achieved by using sheets of transfer film 905.As an alternative, transfer film 905 may be provided in a continuousform, such as a continuous roll, in which case, a portion of thecontinuous roll may be placed in position to be processed, as shown inFIG. 9, and once the portion in position is processed, the roll can beindexed forward to place an unprocessed portion of the roll in positionfor processing.

In some applications, it may be desirable or necessary to carry out atransfer of a transferable material from carrier film 920 to substrate270 in an inert environment, meaning, for example, in argon or nitrogenenvironment rather than, for example, in air. This may be so becausetransferable film 905 may include materials or layers that may, forexample, undergo an undesirable chemical reaction in the presence of,for example, oxygen when illuminated with sufficiently intense light.Furthermore, in some applications, some or all handling, includingprocessing, of transfer film 950 may need to be performed in an inertenvironment.

All patents, patent applications, and other publications cited above areincorporated by reference into this document as if reproduced in full.While specific examples of the invention are described in detail aboveto facilitate explanation of various aspects of the invention, it shouldbe understood that the intention is not to limit the invention to thespecifics of the examples. Rather, the intention is to cover allmodifications, embodiments, and alternatives falling within the spiritand scope of the invention as defined by the appended claims.

1. An optical imaging system for selective thermal transfer of amaterial from a donor film to a substrate, the optical imaging systemcomprising: a light source capable of emitting a patterned light beam,the patterned light beam including two or more emitted light segments,each emitted light segment having a first uniformity along a firstdirection; a light homogenizer receiving the two or more emitted lightsegments from an input face of the light homogenizer, the lighthomogenizer homogenizing each emitted light segment and transmitting acorresponding homogenized light segment from an output face of the lighthomogenizer, each transmitted homogenized light segment having a seconduniformity along the first direction, the second uniformity of eachtransmitted homogenized light segment being greater than the firstuniformity of each corresponding emitted light segment; a first maskhaving at least twenty optically transmissive areas, each opticallytransmissive area having a length along the first direction that variesbetween first and second values and a height along a second direction,the first mask receiving and patterning each transmitted homogenizedlight segment into a row of at least twenty discrete light subsegmentsalong the first direction; and a lens system projecting light patternedby the mask onto a transfer plane so as to form a projected array ofdiscrete projected light segments in the transfer plane, such that whena donor film that includes a transferable material disposed proximate acarrier, is placed proximate a substrate that lies in the transferplane, each of the discrete projected light segments is capable ofinducing a transfer of the transferable material from the carrier ontothe substrate.
 2. The optical imaging system of claim 1, wherein thelength of each optically transmissive area varies continuously betweenthe first and second values.
 3. The optical imaging system of claim 1,wherein the length of each optically transmissive area varies indiscrete steps between the first and second values.
 4. The opticalimaging system of claim 1, wherein an internal optical transmittance ofeach optically transmissive area is at least 99.9%.
 5. The opticalimaging system of claim 1 further having a second mask disposed betweenthe light homogenizer and the first mask.